Nanoscale Barrier Layers to Enable the Use of Gallium-Based Thermal Interface Materials with Aluminum
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JMEPEG https://doi.org/10.1007/s11665-020-05007-1
Nanoscale Barrier Layers to Enable the Use of Gallium-Based Thermal Interface Materials with Aluminum Stephen Stagon
, Neil Blaser, Grant Bevill, and John Nuszkowski
(Submitted May 5, 2020; in revised form June 3, 2020) Performance of thermal interface materials (TIMs), such as thermal pastes and mats, hinders the advance of integrated circuit (IC) devices. Current state-of-the-art TIMs suffer from low thermal conductivity, thick cross sections, and poor long-term performance. Gallium (Ga) and gallium-based alloys and amalgamations, in liquid and solid form, have demonstrated up to three times greater thermal conductivity than conventional TIMs, but rapidly alloy with and destroy aluminum (Al) components, which are commonly found in IC devices. In this work, we investigate the use of thin-film barrier layers on Al to prevent Ga alloying and characterize their performance through accelerated Ga exposure experiments and scanning electron microscopy. It is found that 100-nm-thick layers of the common passivation materials niobium and 304 stainless steel do not sufficiently prohibit Ga migration, but a 100 nm layer of titanium (Ti) does. No alloying is evident in Ti-coated Al samples after exposure to a liquid Ga alloy droplet at 300 °C for 168 h, 250 thermal cycles from room temperature to 150 °C with 30-min dwell, or 50 thermal cycles from room temperature to 300 °C with 2-min dwell. The results present a clear and direct path to the use of Ga and Ga alloys as TIMs through the addition of a thin inexpensive barrier layer on Al components and may enable future IC device technologies. Keywords
barrier layer, liquid metal, physical vapor deposition, thermal interface material, thermal management
1. Introduction As IC devices continue to push toward smaller sizes, higher speeds, and greater power density, demands on thermal management are ever-increasing (Ref 1, 2). TIMs play a key role in thermal management of IC devices through moving heat from the heat generating component to heat mitigation components like spreaders and heat transfer devices such as heat exchangers (Ref 1, 2). Often, the heat mitigation components are made of Al due to its low cost, high thermal conductivity, ease of manufacturing, and corrosion resistance (Ref 3). The most prevalent TIMs are composed of metallic or carbon-based micro- or nanoparticles in an organic binder (Ref 2). Although advantageous due to ease of handling and low cost, these materials are not ideal due to their relatively low thermal conductivity, thick bond cross sections, short service life and low maximum operating temperatures (Ref 2, 4). The overall performance of TIMs on the device scale is composed primarily of thermal performance and lifetime (Ref 1, 2). Important thermal performance parameters are thermal Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11665-020-05007-1) contains supplementary material, which is available to authorized users. Stephen Stagon, Neil Blaser, G
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